feat(lanes): prime and nudge codex lanes into declaring their own stage

A codex lane's declared stage has always depended entirely on the session
reading AGENTS.md and calling `ccam stage` on its own — no hook, no wrapper,
no enforcement. Two additions make that more reliable without touching the
declared-wins / inferred-never-done invariants:

- LaneConsolePane pre-fills a codex pane's opening prompt with a plain-text
  stage-declaration checklist built from the lane's own pipeline_nodes —
  the same up-front priming a Claude lane gets from its pre-filled
  /ccam:ship-feature-lane skill command, just as prose since Codex has no
  slash commands.
- server/lib/codex-nudge.js sweeps every 60s and types a one-line reminder
  into a lane's live tmux pane (tmux.sendText, a new literal-text primitive
  alongside sendCommand) when its fresh detected_stage has sat undeclared
  for over two minutes. It never writes stage/detected_stage itself — any
  resulting declaration is still the codex session's own real ccam stage
  call, just server-prompted instead of relying on memory alone.

server 1354/1354, client 449/449, tsc clean.

server/index.js

@@ -404,6 +404,15 @@ function startBackgroundServices() {
   } catch (err) {
     console.warn("codex poll failed to start:", err.message);
   }
+  // Safety net: a codex lane only declares stage when the session calls
+  // `ccam stage` itself. When auto-detection has clearly moved on without a
+  // matching declaration, nudge the session's own pane to make the real call
+  // — never writes stage itself, so the declared-wins invariant is untouched.
+  try {
+    require("./lib/codex-nudge").startCodexNudge();
+  } catch (err) {
+    console.warn("codex nudge failed to start:", err.message);
+  }
   // Continuous discovery of sessions under ~/.claude/projects. The one-time
   // legacy backfill above runs only once (marker-gated), so a project added
   // later whose sessions never flow through hooks would otherwise stay invisible